Causes of Bipolar Disorder|Genes - The key Player

Wondering what are the causes of bipolar disorder?

Today’s medicine is advanced but sometimes, it struggles to give complete and satisfying answers about the causes and development of certain disorders, same is true for the bipolar disorder.

Why is it important to know the cause? Because the treatment of anything rests on addressing the cause.

Genes - The Key Players

Gender predisposes you to the development of the bipolar disorder. Bipolar disorder is of two main types namely the bipolar I disorder and the bipolar II disorder.

The bipolar I disorder effects both women and men at the same rate. However, bipolar II disorder is more common in women.

Women are more predisposed to developing the bipolar II disorder probably due to the genetics. Gender is a predisposing factor not a cause.

Genes are considered to be the key players in the development of the bipolar disorder. But no single gene is responsible for the disorder. It is a constellation of genes, a group , a complex ,probably and their interactions with each other and with other internal and external factors that leads to the bipolar disorder.

In Nutshell| Causes of Bipolar Disorder

✓ Females are more prone to bipolar II disorder.
✓ Genes play the major role in the causation of bipolar disorder.
✓ Tryptophan hydroxylase 2 gene that codes the enzyme for serotonin synthesis is involved.
✓ CACNA1C gene that codes the calcium channels is involved.
✓ Impaired functioning of the serotonin receptors.
✓ Structural variations can be present like the immature dentate gyrus.

TPH2 Gene and Serotonin Synthesis

Neurotransmitter systems (the system of chemicals in the brain) play a significant role in the development of the disorder. But this is again indirect. The genes responsible for the production of these chemicals (neurotransmitters) undergo some changes and this leads to the impaired functioning of these chemicals.

Tryptophan hydroxylase 2 gene, also known as (TPH2) gene is said to be part of the development of the disorder. This gene is responsible for the synthesis of the tryptophan hydroxylase. This is the main enzyme in the pathway which makes serotonin. Serotonin is one of the hormones, which are responsible for mood changes.

Also, this hormone regulates the day/night circle. That is why, if the hormone is reduced or increased, behavioral changes will be observed in the patient.

Increased quantities of this hormone are associated with manic periods or hypomanic periods. In this situation, the patient feels excited and he/she does not need to sleep. He has high goals and great self-esteem.

The decreased quantities of serotonin, lead to depression, which is the other specific set of symptoms, characteristic for bipolar disorder. Patients feel sleepy and they have low self-esteem. In most cases, they have suicidal thoughts and they feel unworthy.

CACNA1C gene and Calcium Channels Synthesis

The gene- CACNA1C could also be pointed as one of the causes of bipolar disorder. This gene codes the information for the synthesis of substantial calcium channel. This channel is important for conducting the impulses from one neuron to another.

It is estimated that Lithium down regulates the quantity of these calcium channel and this is the reason why patients are well influenced by a lithium therapy. The studies have been carried out on mice and their brains were used to get the required information.

Changes in the Brain Structure - The Immature Dentate Gyrus

Changes in the structure of the brain that are variation from normal can also be the cause of bipolar disorder. Research is going on to find out clues on this aspect. One such clue indicates the possibility of the presence of immature cells in some parts of the brain that effect mood.

There is the of presence of immature dentate gyrus (part of the brain) in persons suffering from bipolar disorder. Elevated levels of a certain chemical (calretinin) have been found in the dentate region of the brain in people suffering from bipolar disorder.

It suggests the presence of immature cells in this area which are producing these chemicals. It implies that there may be structural variations in the brain of the individual suffering from bipolar disorder.

Impaired Serotonin Receptors

Impaired functioning of the serotonin receptors is also considered a cause of bipolar disorder. Receptor is the place on the cell where a certain chemical binds. The place where serotonin binds on the cell is called the serotonin receptor.

Serotonin is an important chemical in controlling our mood. When the chemical binds on the cell, series of changes occurs in the cell and the corresponding response of the chemical is produced. Some studies suggest that the serotonin type 3 receptors (5-HT(3)) are not functioning properly in the individuals suffering from bipolar disorder.

Finding the causes of bipolar disorder is particularly important from the treatment point of view. Once the cause is known measures can be taken to address it and cure the disease. With on going research hopefully we better understand bipolar disorder and come up with better treatment options in the future.


Walton NM, Zhou Y, Kogan JH, Shin R, Webster M, Gross AK, Heusner CL, Chen Q, Miyake S, Tajinda K, Tamura K, Miyakawa T, Matsumoto Walton NM,M. (2012). Detection of an immature dentate gyrus feature in human schizophrenia/bipolar patients. Retrieved from

Hammer C, Cichon S, Mühleisen TW, Haenisch B. (2012). Replication of functional serotonin receptor type 3A and B variants in bipolar affective disorder: a European multicenter study. Retrieved from

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